Why are there no .gif's with sound?

And when are we getting them?

>>10
AC3
Please don't do that.

FLAC, wavpak, Monkey's Audio, many others
Please use only FLAC (or wavpak is you must). Do not use Monkey's Audio (or any others) under any circumstances.

Vorbis compresses slightly better than AAC
Not really. The best AAC encoders available today will generally outperform aoTuV at any bitrate, specially at very low ones if the High Efficiency extensions are used.

That said, and unlike Theora, Vorbis is a fine choice and the differences are not fundamental.

AVC1
Pig disgusting Windows FOURCC. It's just AVC